Tools like PageSpeed Insights, Pingdom Tools and WebPagetest are common to monitor website speed. But unfortunately they were not created for the modern web.
One important thing we need to take into account when using tools for measuring effects, is that we need to compare with tools that support HTTP/2. Otherwise the measured results won’t identify the benefits of using HTTP/2.
However, there are very few such tools publicly available and many of the existing tools for measuring performance have limitations. For example, PageSpeed does not actually measure speed, something you can read about in the below article.
Another popular tool is Pingdom, although it is only using HTTP/1.1 only for the tests, and does not support the same compression formats in the browsers, in particular Brotli.
So it is worth noting that there are some serious limiations with the tools people commonly use for testing performance. There are also several articles discussing these challenges that might be of interest, see for example:
The benefits of using HTTP/2 and push is something that is starting now, and more of the tools are not yet prepared for it. However, HTTP/2 is a technology for today, and it will be the one way to go for an e-commerce that wants to be able to grow in the future, and we have the knowledge to help with that to create faster websites.